1. Introduction
2. Getting Started
3. Hardware Requirements
4. Installation
5. Interface Overview
6. Transport & Playback
7. Pages & Navigation
8. TB-303 Synthesizer
9. Pattern Editing
10. Drum Sequencer
11. Song Mode
12. Project Management
13. Recording Audio
14. Keyboard Shortcuts Reference
15. Mouse Controls

MiniAcid is a portable acid groovebox for the M5Stack Cardputer and web. It combines two squelchy TB-303 style bass synthesizers with a punchy TR-808 inspired drum machine, giving you a complete rhythm production tool in your pocket.

• Two TB-303 voices with full filter, envelope, and effects controls
• Eight-voice drum machine with classic 808 sounds (kick, snare, hats, toms, rim, clap)
• 16-step sequencer for each voice
• Pattern banks with 8 slots per instrument
• Per-pattern automation for 303 and drum parameters
• Multiple drum kits (808/909/606) with per-pattern automation
• Song mode for arranging patterns into complete tracks
• Live muting for all voices
• Audio recording to WAV files
• Scene management with save/load functionality
• Cross-platform: runs on M5Stack Cardputer, and web browsers

1. Power on your M5Stack Cardputer/open MiniAcid in your web browser
2. Press SPACE to start playback
3. Use [ and ] to navigate between pages
4. Use 'ESC' to open the help page for keyboard shortcuts on each page
5. Adjust parameters using the keyboard shortcuts
6. Press SPACE again to stop (auto-saves to SD card if available)

Go to https://miniacid.mrbook.org

1. Search for "MiniAcid" in Launcher or M5Burner
2. Install and run

The MiniAcid interface consists of several sections:

┌─────────────────────────────────────┐
│ TRANSPORT BAR (BPM, Play indicator) │
├─────────────────────────────────────┤
│                                     │
│          PAGE CONTENT               │
│       (varies by active page)       │
│                                     │
├─────────────────────────────────────┤
│    MUTE SECTION (Voice status)      │
└─────────────────────────────────────┘

• Shows page title
• Shows current BPM
• Play/stop indicator (blue in Pattern mode, yellow in Song mode)

• Main content area that changes based on the active page
• Displays parameters, patterns, sequencer grids, or waveforms

• Shows mute status for all voices
• Visual indicators: dimmed = muted, bright = active

MiniAcid has several pages accessible via [ and ] keys:

1. TB-303 Page (A) - First bass synth parameters and waveform
2. Pattern Edit Page (A) - 303A sequencer editor + automation subpage
3. TB-303 Page (B) - Second bass synth parameters and waveform
4. Pattern Edit Page (B) - 303B sequencer editor + automation subpage
5. Drum Sequencer - Drum pattern editor + settings + automation subpages
6. Song Mode - Pattern arrangement and song sequencing
7. Project Page - Scene management and settings
8. Help Page - Keyboard shortcuts and controls

Use CTRL/CMD+UP/DOWN to switch subpages when a page has multiple views (303 pattern automation and drum settings/automation).

Play/Stop: Press SPACE

• Starts playback from the current position
• Stopping automatically saves the scene
  • Cardputer: It saves to SD card (if available)
  • Web: Saves to browser local storage

Adjust BPM:

• K - Decrease BPM by 5
• L - Increase BPM by 5
• Range: typically 60-200 BPM

MiniAcid has two playback modes:

1. Pattern Mode (default, blue indicator)

   • Plays the currently selected pattern for each instrument
   • Each voice loops its active pattern independently

2. Song Mode (yellow indicator)

   • Plays the song arrangement from the Song page
   • Patterns change automatically according to song positions

You can toggle between modes using Ctrl/Cmd + P or by pressing M on the Song page.

MiniAcid features two independent TB-303 style bass synthesizers (303A and 303B). Each has its own parameter page and pattern editor.

Each 303 voice has the following controls:

• Cutoff - Filter cutoff frequency (controls brightness)

  • A - Increase cutoff
  • Z - Decrease cutoff

• Resonance - Filter resonance (controls emphasis/squelch)

  • S - Increase resonance
  • X - Decrease resonance

• Filter Type - LP/BP/HP filter models

  • Focus FLT with LEFT/RIGHT, then use UP/DOWN to change

• Env Amount - Envelope modulation depth

  • D - Increase envelope amount
  • C - Decrease envelope amount

• Decay - Envelope decay time

  • F - Increase decay
  • V - Decrease decay

• Waveform - Oscillator waveform type
  • Options: Saw, Square, Pulse (various widths)
  • T / G cycles waveform (or focus OSC and use UP/DOWN)

• Delay - Tempo-synced delay effect

  • M - Toggle delay on/off

• Tube Distortion - Saturation/overdrive effect

  • N - Toggle distortion on/off

On the 303 parameter pages, you can use the mouse to adjust knobs:

• Click and drag on a knob to adjust value
• Scroll wheel over a knob for fine adjustment

Each 303 voice has a dedicated pattern editor page with:

• Two rows of 8 steps (16 steps total)
• Note display for each step
• Slide and accent indicators
• Pattern bank selector (8 pattern slots)

Move Between Steps:

• Arrow keys or Cardputer arrow cluster (; , . /)
• Selected step highlighted with a border

Move Between Rows:

• UP/DOWN arrows

Pattern Selection:

• When cursor is on the patterns row, Q through I - Select pattern slots 1-8
• ENTER - Load the highlighted pattern (when on pattern row)

When a step is focused:

Note Editing:

• A - Increase note by one semitone
• Z - Decrease note by one semitone
• Range: C1 to B4 (4 octaves, including sharps)

Octave Change:

• S or ALT+UP - Increase octave
• X or ALT+DOWN - Decrease octave

Modifiers:

• Q - Toggle slide (glide to next note)
• W - Toggle accent (emphasis/louder)

Clear Step:

• BACKSPACE - Clear the step (no note plays)

• Note box - Large square showing note value (e.g., "C#2")
• Slide indicator - Small colored box above note (green)
• Accent indicator - Small colored box above note (yellow)
• Current step - Border around the selected step

Each 303 voice has 8 pattern slots:

• Switch between slots using Q-I keys
• Each slot stores a complete 16-step pattern
• Active pattern number shown at top of page
• Bank selection bar shows all 8 slots

Copy/Paste:

• CTRL+C or CMD+C - Copy current pattern
• CTRL+V or CMD+V - Paste pattern to current slot
• CTRL+X or CMD+X - Cut pattern (copy and clear)

Undo:

• CTRL+Z or CMD+Z - Undo last edit

Transpose:

• ALT+D - Transpose pattern up one semitone
• ALT+C - Transpose pattern down one semitone

Rotate:

• ALT+F - Rotate pattern forward by one step
• ALT+V - Rotate pattern backward by one step

Each 303 pattern has an automation subpage for parameter lanes (cutoff, resonance, envelope, oscillator, filter type, volume).

Open the Automation Subpage:

• CTRL/CMD+UP or CTRL/CMD+DOWN - Switch between pattern notes and automation
• Click the up/down indicator in the title bar (desktop/web)

Select a Lane:

• TAB / SHIFT+TAB - Move focus between the pattern bar, lane list, and lane editor
• UP/DOWN (when the lane list is focused) - Choose a parameter lane
• ENTER (on a lane label) - Enable/disable that lane

Edit the Lane:

• Arrow keys - Move the cursor
• ENTER - Add/remove a node at the cursor
• BACKSPACE - Delete the node at the cursor
• ALT+LEFT/ALT+RIGHT - Jump between existing nodes

Indicators:

• A small yellow square next to a parameter means that lane has automation
  • Filled = enabled, outline = disabled
• Lanes hold the last node value to the end of the pattern
• Copy/paste/cut operations include automation data for the pattern
• Option-based lanes (oscillator, filter type) use discrete steps per option

• Click on a step to select it
• Click on pattern slots in the bank selector to switch patterns
• Drag across pattern selector for quick switching

The drum sequencer features 8 drum voices arranged in a grid:

• 16 steps per voice
• 8 pattern slots
• Individual voice muting

1. Kick (3) - Bass drum
2. Snare (4) - Snare drum
3. Closed Hat (5) - Closed hi-hat
4. Open Hat (6) - Open hi-hat
5. Mid Tom (7) - Mid tom
6. High Tom (8) - High tom
7. Rim (9) - Rim shot
8. Clap (0) - Hand clap

(Numbers in parentheses are mute keys)

MiniAcid ships with three drum kits inspired by different classic drum machines:

• 808 (default)
• 909
• 606

Move in Grid:

• Arrow keys or Cardputer arrows
• Highlight moves across steps and voices

Pattern Selection:

• Q through I - Select drum pattern slots 1-8
• Pattern row at top shows available patterns

Toggle Hit:

• ENTER - Toggle drum hit on/off at current step
• Active hits shown as filled squares

Toggle Accent:

• W - Toggle accent on/off at current step
• Accents shown as a thin bar above each step (affects all drum voices on that step)

Load Pattern:

• Navigate to pattern row (top of grid)
• Press ENTER to load selected pattern

Switch to the Drum Settings subpage with CTRL/CMD+UP/DOWN.

• KIT - Select 808/909/606 (focus the KIT label, then use UP/DOWN)
• Distortion - A/Z
• Compression - S/X
• Transient Sustain - D/C
• Reverb Mix - F/V
• Reverb Decay - G/B

Automation indicators appear next to parameters that have automation lanes.

Switch to the Drum Automation subpage with CTRL/CMD+UP/DOWN.

Drum automation is per-pattern and includes these lanes:

• KIT (drum engine)
• DIST (distortion)
• COMP (compression)
• SUS (transient sustain)
• RVB (reverb mix)
• RDEC (reverb decay)
• VOL (drum volume)

Use the same lane editor controls as the 303 automation page (see below). Option-based lanes (KIT) use discrete steps per option.

• Click on grid cells to toggle drum hits
• Click on accent lane to toggle accents
• Click pattern slots to switch patterns
• Visual feedback on hover

Song Mode allows you to arrange patterns into complete songs by creating a sequence of song positions. Each position defines which patterns play for all three tracks (303A, 303B, Drums).

• Navigate to the Song Page using [ and ] keys
• The page shows a grid of song positions, reminiscent of a tracker interface

Tracks (columns):

• 303A - First bass synthesizer
• 303B - Second bass synthesizer
• Drums - Drum machine

Positions (rows):

• Song positions 1-128
• Each position can have different pattern assignments
• Length: 1 to 128 positions

Move Selection:

• Arrow keys - Navigate between cells
• UP/DOWN - Move between positions (rows)
• LEFT/RIGHT - Move between tracks (columns) or focus mode toggle

Vertical Scrolling:

• Grid scrolls automatically during playback
• Selected cell is always visible

Assign Pattern to Cell:

• Select a cell (track × position)
• Using ALT + ARROW UP/ARROW DOWN, change the assigned pattern to that cell
• Pattern bank+number appears in cell

Clear Assignment:

• BACKSPACE - Clear pattern from selected cell
• Track will be silent at that position

Change Bank (if supported):

• ALT+UP - Next bank
• ALT+DOWN - Previous bank

Mode Toggle:

• M or ENTER (on mode indicator) - Toggle between Song Mode and Pattern Mode

Pattern Mode (blue indicator):

• Plays currently selected patterns continuously
• Pattern selection on 303/drum pages determines what plays

Song Mode (yellow indicator):

• Plays song arrangement sequentially
• Pattern changes according to song grid
• Playhead indicator shows current position

Playhead Navigation (during playback):

• ALT+UP - Jump to next position
• ALT+DOWN - Jump to previous position

• Default: 1 position
• Automatically extends when you edit positions beyond current length
• Maximum: 128 positions

When Song Mode is active:

• Transport bar shows yellow indicator
• 303 and drum pages display the pattern currently playing at the current song position
• Pattern editors still work normally for editing individual patterns

A Scene contains your complete project state:

• All pattern banks (303A, 303B, Drums)
• All 303 parameter settings (filter, envelope, effects)
• Song arrangement
• Mute states

Auto-Save:

• Scene automatically saves when you stop playback (press SPACE)
• Requires SD card on Cardputer

Manual Save:

• CTRL+S or CMD+S - Save scene immediately

• On startup, MiniAcid loads the last saved scene from SD card
• If no scene exists, loads default patterns

Cardputer:

• Saves to SD card root. For example: /miniacid_scene.json

Web Browser:

• Uses browser local storage
• Persists between sessions

MiniAcid can record your sessions to WAV audio files. Recording captures the master output including all voices, live changes and effects.

Keyboard Shortcut:

• CTRL+R or CMD+R - Start recording

What Happens:

• Recording indicator appears (red square) in the transport bar
• Audio begins writing to WAV file
• All generated audio is captured in real-time

Keyboard Shortcut:

• CTRL+R or CMD+R again - Stop recording
• Or press SPACE to stop playback (also stops recording)

• Sample Rate: 22050 Hz (22.05 kHz)
• Bit Depth: 16-bit PCM
• Channels: Mono
• Format: WAV (uncompressed)

Cardputer:

• Saves to SD card: /miniacid_YYYYMMDD_HHMMSS.wav
• Example: miniacid_20260109_143045.wav

Web Browser:

• Automatically downloads when recording stops
• Filename: miniacid_recording.wav

• Start playback first, then start recording for a clean start
• Let patterns loop at least once for complete bars
• Stop recording cleanly using the keyboard shortcut
• Check SD card space on Cardputer before long recordings
• Typical file size: ~1.3 MB per minute of audio

Available in Desktop/Web versions

Knob Interaction:

• Click and drag - Adjust parameter value
  • Drag up to increase, down to decrease
  • Smooth, continuous control
• Mouse wheel - Fine adjustment
  • Scroll up to increase, down to decrease
  • Precise value changes
• Visual feedback - Knob updates in real-time

Step Selection:

• Click on step - Select that step for editing
• Visual highlight - Shows selected step

Pattern Bank:

• Click on pattern slot - Switch to that pattern
• Active pattern - Highlighted in bank selector

• Click in the automation lane editor - Add/remove nodes
• Click the yellow square next to a lane label to enable/disable automation

• Click in the automation lane editor - Add/remove nodes
• Click the yellow square next to a lane label to enable/disable automation

Grid Editing:

• Click on cell - Toggle drum hit on/off
• Click and drag - Paint multiple hits (if supported)
• Hover effect - Visual feedback before clicking

Cell Selection:

• Click on cell - Select position/track
• Visual highlight - Shows selected cell

Pattern Assignment:

• Use keyboard after clicking cell to assign patterns

Bank Selection Bar:

• Click on bank - Switch to that bank
• Visual indicator shows active bank

Pattern Selection Bar:

• Click on pattern - Load that pattern
• Active pattern highlighted

1. Start simple - Use 4-8 notes, not all 16 steps
2. Use slides - The "acid" sound comes from sliding between notes
3. Add accents - Emphasize certain beats (1 and 3, or syncopated)
4. Cutoff and resonance - High resonance + moving cutoff = squelch
5. Envelope modulation - Moderate env amount (200-600) sounds natural
6. Randomize and edit - Press I or O to generate ideas, then refine

1. Four-on-floor - Kick on every beat (steps 1, 5, 9, 13)
2. Snare backbeat - Snare on 2 and 4 (steps 5, 13)
3. Hat patterns - Closed hat every other step for energy
4. Open hats - Use sparingly for emphasis and release
5. Randomize for variety - Press P then edit to taste

1. Live muting - Use number keys to drop voices in/out
2. Parameter tweaking - Adjust filter cutoff while playing
3. Pattern switching - Change patterns on-the-fly (switches at next loop)
4. BPM changes - Gradually increase tempo for energy
5. Effects - Toggle delay/distortion for texture changes

Happy acid jamming! 🎵🎛️🔊